1. Field of the Invention
The present invention relates to an apparatus and a method for generating a Gamma voltage, and more particularly to an apparatus and a method for dynamically correcting a Gamma voltage.
2. Description of Related Art
Image devices have been widely used in different products. For these image devices, Gamma generators usually are used in internal circuits thereof. For example, when liquid crystals are driven to display image on a liquid crystal display, a driving voltage should be applied so as to tilt the liquid crystals for a desired angle. Usually, the driving voltage is controlled by image signals, e.g. digital signals. The relationship among the image signals, the driving voltage, the tilt angle of the liquid crystals and pixel transparence are not lineal. Therefore, Gamma generators are required to correct the driving voltages, i.e. the Gamma curve, of the image signals.
FIG. 1 is a circuit block diagram showing a prior art liquid crystal display. Referring to FIG. 1, the prior art circuit comprises a timing controller 110, a Gamma generator 120, a display driving circuit 130 and a liquid crystal display 140. The timing controller 110 receives the image data 101, and then outputs the image data 111 and the timing control signal 112. The Gamma generator 120 provides Gamma voltages 121 corresponding to different gray levels. The display driving circuit 130 comprises a data-line driver 131 and a scan-line driver 132. The scan-line driver 132 generates driving signals according to the timing control signal 112 so as to drive scan lines of the liquid crystal display panel 140. The data-line driver 131 locks the image data 111 according to the timing control signal 112. The data-line driver 131 selects and outputs a Gamma voltage corresponding thereto so as to drive the data lines of the liquid crystal display 140.
Generally, a series of resistors are used to divide the voltage to generate the Gamma voltages. It means that the Gamma voltages are fixed and cannot be changed. If the Gamma voltages or the Gamma curves are fixed, it is difficult to distinguish the contrast of different darkness when the image tends to be slightly darker. Likewise, it is difficult to distinguish the contrast of different brightness when the image tends to slightly brighter. This phenomenon will adversely affect the image quality.